The present invention relates to the image processing arts. It finds particular application in conjunction with controlling the acquisition of diagnostic images acquired in a plurality of modes and will be described with particular reference thereto. However, it is to be appreciated that the invention is also applicable to other fields where images are acquired with multiple clock rates.
Conventionally, multi-mode imaging systems could process digitally only images acquired in a mode synchronous with that of a system reference signal. Image data acquired in acquisition modes asynchronous to the reference signal were directly displayed without the benefit of digital processing. In conventional imaging systems, when an operator changes the x-ray exposure for image acquisition, the system continues to acquire and/or display all images during the period of transition from the original rate to the new rate, whether the images are properly exposed or not. When the end of an imaging run is completed by the deactivation of a foot switch or a hand switch, the frame being acquired when deactivation occurs is always discarded to avoid the possibility of displaying an underexposed image.
In conventional multi-mode acquisition x-ray systems, data acquired during an asynchronous acquisition mode is sent from the acquiring camera directly to a display, without digital image processing. The asychronously acquired image data causes flickering on the monitor in a degree according to the operating exposure rate. Additionally, due to this direct passing of the image data, when image acquisition operations cease, the display will become blank, not holding the last image. Further, since the conventional x-ray imaging system continues to display and/or acquire all images during the transition from one exposure rate to another, a disruption in the flow of valid images on the display takes place. The improperly exposed images acquired during the transition are displayed. Also, since the last image in a run is automatically discarded without checking its validity, there is a likelihood that valid images containing valuable information are discarded.
In accordance with the present invention, a unified apparatus and method are provided to acquire good x-ray video images regardless of the acquisition mode and exposure rate.